The present invention relates to a canister structure which comprises a canister body operative to trap fuel vapor evaporating in a fuel tank and supply the trapped fuel vapor to an intake system of an internal combustion engine of a vehicle and an outside-air connection pipe coupled to the canister body so as to open into an outside air at a fresh-air inlet thereof, the outside-air connection pipe interconnecting the inside of the canister body and the outside air.
In general, the canister comprises the canister body which accommodates a fuel-vapor trap, such as active carbon, and traps the fuel vapor which evaporates in the fuel tank with the fuel-vapor trap. Herein, the air excluding the fuel vapor is released into the outside air (atmosphere) via the outside-air connection pipe which is coupled to the canister body. In some case, the outside air may come into the fuel tank via the outside-air connection pipe and the canister body in accordance with the pressure change due to the temperature change of the inside the fuel tank.
Further, the canister body supplies the trapped fuel vapor to the intake system of the engine in accordance with the engine operation condition. Namely, the canister body is coupled to the engine intake system (intake pipe) via a purge pipe, a purge control valve operative to open or close in accordance with the engine operation condition is provided in the purge pipe. When the purge control valve opens, the inside pressure of the canister body and the outside-air connection pipe becomes a negative pressure, so that the outside air comes into the outside-air connection pipe via the fresh-air inlet of the outside-air connection pipe. Accordingly, the mixture of the outside air and the fuel vapor is supplied to the engine intake system.
Herein, there is a concern that if the water comes into the outside-air connection pipe via the fresh-air inlet, the capacity of the fuel-vapor trap would deteriorate due to the water reaching the canister body and the water would further reach the engine improperly. Therefore, it may be necessary to prevent the water from coming into the canister body properly.
Herein, Japanese Utility Model Laid-Open Publication No. 4-129868 discloses a canister structure in which the outside-air connection pipe is coupled to one end of an engine mount member with a hollow portion which comprises a horizontal center portion and both end portions which extend obliquely upward from the horizontal center portion respectively, thereby preventing the water from coming into the canister body even if the horizontal center portion is covered with water.
The canister structure of the above-described publication, however, may function properly only in a particular case in which the water level when the horizontal center portion is covered with water is considerably low. This structure could not cope with a situation in which the water level is rather higher (for example, at the level of two third of the height of a vehicle wheel).
Other Japanese Patent Laid-Open Publication Nos. 63-162329, 2001-152972 and 2004-346801 also disclose different canister structures respectively. However, these canister structures would not be sufficient yet in terms of surely preventing the water from coming in.